Patients with deep vein thrombosis of the lower extremities andor pelvis are eligible for this protocol if their thrombosis has been symptomatic for no more than 14 days and if their bleeding risk is very low. They are hospitalized for 3-7 days for up to 4 daily injections of rtPA directly into their thrombi. Simultaneously they receive anticoagulation, which is continued for 6 months. Last year we completed the treatment phase of the protocol after accrural of the 30th patient. Extensive thrombolysis had been achieved with low doses of alteplase in every patient, and there have been no serious adverse events. As the protocol is approved for 30 patients , we have completed accrural of patients for the protocol. Although no new patients can be recruited, the protocol now enters follow up phase that last 5 years for each patient. During this follow up period we are permitted to treat the first recurrence of DVT in a previously treated protocol patient if the patient returns to us when 14 days of onset of symptoms. this allows us to get precise evaluation of extent of DVT if a recurrence occurs. Two years ago , we reported successful treatment of a recurrence in a 21yo WM , who 2year after initial treatment developed recurrent extensive DVT during convalescence after ORIF for a fibula fracture. Since that case, we have not heard of any other cases of recurrent DVT in any other previously treated protocol patient. We are hoping to get funding to support a study of incidence of post thrombotic syndromes in these patients.